1. Field of the Invention
The present invention relates generally to a fluid compressing apparatus, and more particularly, to a fluid compressing apparatus for discharging the fluid by a compressing or pumping action utilizing a linear reciprocating movement of a piston.
2. Description of the Related Art
A typical example of a conventional fluid compressing apparatus is shown in FIGS. 1 and 2, which will be described briefly below.
FIGS. 1 and 2 are sectional views that schematically show the structure and operation of the conventional fluid compressing apparatus. The reference numeral 10 indicates a cylinder block, 20 a piston, 30 a valve plate and 40 a cylinder head.
As shown in FIGS. 1 and 2, the cylinder block 10 has a cylinder bore 11 of a predetermined diameter that penetrates through the cylinder block 10 in a lengthwise or longitudinal direction. The piston 20 is movably mounted in the cylinder bore 11 of the cylinder block 10 so as to be capable of reciprocal action, and the valve plate 30 is disposed in the cylinder block 10. The valve plate 30 has fluid suction/discharge ports 31 and 32 formed therein, and suction/discharge valves 33 and 34 (shown in phantom), that can open and cover the fluid suction/discharge ports 31 and 32. The cylinder head 40 is disposed in the cylinder block 10 toward the longitudinal side adjacent the valve plate 30, and the cylinder head 40 has fluid suction/discharge chambers 41 and 42 respectively interconnecting with the fluid suction/discharge ports 31 and 32 of the valve plate 30. The cylinder head 40 is connected to fluid suction/discharge manifolds 43 and 44 that are respectively interconnected with the fluid suction/discharge chambers 41 and 42 of the cylinder head 40.
In the conventional fluid compressing apparatus constructed as described above, and illustrated in FIGS. 1 and 2, a driving force transmitted from a piston driving source (not shown), causes the piston 20 to reciprocate within the cylinder bore 11 of the cylinder block 10, thereby causing the fluid to be drawn in, compressed and discharged.
Additionally, as the piston 20 moves from the top dead end point T (FIG. 1) to the bottom dead end point B (FIG. 2) of the cylinder bore 11, due to the different pressures in and out of the cylinder bore 11, the suction valve 33 opens the suction port 31 of the valve plate 30 (as shown in phantom in FIG. 2), and accordingly, the fluid is drawn into the cylinder bore of the cylinder block 10 sequentially through the suction manifold 43, the suction chamber 41 of the cylinder head 40 and the suction port 31 of the valve plate 30. At this time, the pressure in the discharge chamber 42 of the cylinder head 40 is higher than the pressure in the cylinder bore 11 so that the discharge valve 34 maintains the discharge port 32 closed.
Meanwhile, as the piston 20 is returned from the bottom dead end point B (FIG. 2) to the top dead end point T (FIG. 1), the fluid in the cylinder bore 11 is gradually compressed. Finally, when the piston 20 reaches the top dead end point T, as shown in FIG. 1, the pressure in the cylinder bore 11 becomes higher than the pressure in the discharge chamber 42 of the cylinder head 40, and accordingly, as shown in phantom in FIG. 1, the discharge valve 34 opens the discharge port 32 of the valve plate 30, and the compressed fluid is discharged through the discharge port 32 of the valve plate 30, the discharge chamber 42 of the cylinder head 40 and the discharge manifold 44. At this time, the pressure in the suction chamber 41 is lower than the pressure in the cylinder bore 11, and thus, the suction valve 33 maintains the suction port 31 closed.
Then, when the piston 20 moves back to the bottom dead end point B, the suction port 31 is opened by the suction valve 33, whereas the discharge port 32 is closed by the discharge valve 34. As a result, the fluid is drawn into the bore 11. Then as the piston 20 is moved to the top dead end point T, the drawn air is compressed and then discharged through the discharge port 32. As this reciprocating movement of the piston 20 repeats, the compression and discharge of the fluid also repeats the cycle described above.
In the conventional fluid compressing apparatus described above, however, the compressed fluid is often incompletely discharged, which retains some residual fluid at the discharge port 32 of the valve plate 30. Such residual fluid re-expands during the fluid suctioning process in which the piston 20 is moved from the top dead end point T to the bottom dead end point B. The problem arises in the initial fluid suctioning process where the piston 20 is moved toward the bottom dead end point B. That is, due to the presence of re-expanding residual fluid, the pressure in the cylinder bore 11 is initially higher than the pressure in the suction chamber 41, although the pressure in the cylinder bore 11 is lower than the pressure in the discharge chamber 42 of the cylinder head 40. Accordingly, the suctioning does not occur at the beginning of the stroke of the piston 20 toward the bottom dead end point B. Then the suction valve 33 is opened to draw in the fresh fluid when the pressure in the cylinder bore 11 becomes lower than the pressure in the suction chamber 41, which is obtained only when the piston 20 moves toward the bottom dead end point B for a sufficient period of time. In other words, the residual fluid from the fluid compression and discharge in the conventional fluid compressing apparatus causes a clearance volume in the cylinder bore 11 that makes a certain space in the cylinder bore 11 unavailable. Accordingly, the amount of drawn fluid decreases, and pumping efficiency deteriorates considerably.
Further, due to the complicated structure that is used for the suction valve 33 and the discharge valve 34 for opening/closing the fluid suction port 31 and discharge port 32, the conventional apparatus is difficult to assemble and productivity thus deteriorates, and manufacturing costs increase considerably.
The present invention has been made to overcome the above-mentioned problems of the related art, and accordingly, it is an object of the present invention to provide a fluid compressing apparatus for increasing pumping efficiency by discharging compressed fluid completely out of the bore and thus minimizing clearance volume in the cylinder bore.
Another object is to provide a fluid compressing apparatus having a simple structure and being easy to assemble and thereby increasing productivity and reducing manufacturing costs, by using a piston to open and close a fluid suction port, thereby omitting a need to use a separate suction valve device, and providing a discharge valve device having a simple structure.
The above objects are accomplished by providing a fluid compressing apparatus according to the present invention, including a cylinder block having a cylinder bore of a predetermined diameter penetrating through the cylinder block in a lengthwise direction, a discharge chamber having a diameter larger than the diameter of the cylinder bore, and at least one fluid suction port penetrating in the cylinder block in a substantially perpendicular direction with respect to the cylinder bore, the cylinder block using a certain space thereof that is interconnected with the discharge chamber of the cylinder borer as a fluid discharge port; a piston movably disposed in the cylinder bore of the cylinder block to be linearly reciprocated; a discharge valve assembly having a valve plate disposed to be resiliently biased from the discharge chamber toward the fluid discharge port so as to selectively open or close the fluid discharge port of the cylinder block; and a cylinder head disposed at an end of the discharge chamber of the cylinder block, and having a fluid discharge channel interconnected with the discharge chamber.
According to the present invention, the fluid is drawn when the fluid suction port is selectively opened by the linear reciprocation of the piston within the cylinder bore of the cylinder block, and discharged when the fluid discharge port is opened by the valve plate that is separated from the fluid discharge port by the high pressure of the fluid in the cylinder bore caused by the reciprocating piston. Since suction valves having complicated structure are omitted, ease of assembly and improved productivity are achieved, and manufacturing costs are reduced. Also, since the high pressure fluid, compressed in the cylinder bore, is discharged through the fluid discharge port completely, a clearance volume in the cylinder bore can be avoided or minimized, and thus, the compression efficiency is enhanced.
In the fluid compressing apparatus according to the preferred embodiment of the present invention, a top dead end point of the piston is slightly beyond an extreme end of the cylinder bore, thereby discharging the fluid compressed in the cylinder bore completely when the piston contacts the valve plate.
The fluid suction port is positioned adjacent a bottom dead end point of the piston, i.e., adjacent to an extreme end point for the movement of the piston, so that the fluid suction port is instantly opened when the piston reaches the bottom dead end point and a fluid is drawn rapidly through the open fluid suction port.
The discharge valve assembly includes the valve plate disposed to be separable and floatable from the fluid discharge port of the cylinder block, and having a first boss formed approximately at a center of one side; a supporting plate disposed in the discharge chamber of the cylinder block at a predetermined distance from the valve plate, the supporting plate having a second boss formed at one side corresponding to the first boss, and a plurality of fluid passages formed around the second boss in a radial direction; and an resilient member disposed between the valve plate and the supporting plate, for resiliently biasing the valve plate toward the fluid discharge port.
The cylinder block has a circular or a rectangular outer structure. Two fluid suction ports can be provided to the cylinder block and these may be diametrically opposed to each other. Alternatively, more than two fluid suction ports can be provided to the cylinder block disposed at a predetermined space from each other.
The fluid suction port can be tapered, or formed into a double-layered structure consisting of a large diameter portion and a smaller diameter portion, or formed as a combination of the tapered and double-layered structure.
The area of the fluid suction port utilized for drawing the fluid is preferably widened by cutting away at least a certain portion of the cylinder block, for more efficient drawing of the fluid.